Nuclear phosphoprotein kinase activities in normal and neoplastic tissues.

Nuclear phosphoprotein kinases from normal rat liver and transplantable neoplasms were fractionated and compared. A phosphoprotein kinase fraction activated by Mn2+ was found to be present only in the neoplasms. This nuclear protein kinase phosphorylated nuclear proteins represented by one major and several minor bands as determined by polyacrylamide gel electrophoresis (M approximately 50,000).